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Subject[PATCH v2 1/2] gpio: add GPO driver for PCA9570
Date
NXP PCA9570 is 4-bit I2C GPO expander without interrupt functionality.
Its ports are controlled only by a data byte without register address.

As there is no other driver similar enough to be adapted for it, a new
driver is introduced here.

Signed-off-by: Sungbo Eo <mans0n@gorani.run>
---
v2:
* move the direction functions below the set functions
* use devm_gpiochip_add_data() and remove the remove callback

v1:
Tested in kernel 5.4 on an ipq40xx platform.

This is my first time submitting a whole driver patch, and I'm not really familiar with this PCA expander series.
Please let me know how I can improve this patch further.

FYI there's an unmerged patch for this chip.
http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2017-May/105602.html
I don't have PCA9571 either so I didn't add support for it.
---
drivers/gpio/Kconfig | 8 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-pca9570.c | 148 ++++++++++++++++++++++++++++++++++++
3 files changed, 157 insertions(+)
create mode 100644 drivers/gpio/gpio-pca9570.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c6b5c65c8405..d10dcb81b841 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -962,6 +962,14 @@ config GPIO_PCA953X_IRQ
Say yes here to enable the pca953x to be used as an interrupt
controller. It requires the driver to be built in the kernel.

+config GPIO_PCA9570
+ tristate "PCA9570 4-Bit I2C GPO expander"
+ help
+ Say yes here to enable the GPO driver for the NXP PCA9570 chip.
+
+ To compile this driver as a module, choose M here: the module will
+ be called gpio-pca9570.
+
config GPIO_PCF857X
tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
select GPIOLIB_IRQCHIP
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 1e4894e0bf0f..33cb40c28a61 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_OCTEON) += gpio-octeon.o
obj-$(CONFIG_GPIO_OMAP) += gpio-omap.o
obj-$(CONFIG_GPIO_PALMAS) += gpio-palmas.o
obj-$(CONFIG_GPIO_PCA953X) += gpio-pca953x.o
+obj-$(CONFIG_GPIO_PCA9570) += gpio-pca9570.o
obj-$(CONFIG_GPIO_PCF857X) += gpio-pcf857x.o
obj-$(CONFIG_GPIO_PCH) += gpio-pch.o
obj-$(CONFIG_GPIO_PCIE_IDIO_24) += gpio-pcie-idio-24.o
diff --git a/drivers/gpio/gpio-pca9570.c b/drivers/gpio/gpio-pca9570.c
new file mode 100644
index 000000000000..e6b6c4e791c0
--- /dev/null
+++ b/drivers/gpio/gpio-pca9570.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for PCA9570 I2C GPO expander
+ *
+ * Copyright (C) 2020 Sungbo Eo <mans0n@gorani.run>
+ *
+ * Based on gpio-tpic2810.c
+ * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
+ * Andrew F. Davis <afd@ti.com>
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+
+/**
+ * struct pca9570 - GPIO driver data
+ * @chip: GPIO controller chip
+ * @client: I2C device pointer
+ * @buffer: Buffer for device register
+ * @lock: Protects write sequences
+ */
+struct pca9570 {
+ struct gpio_chip chip;
+ struct i2c_client *client;
+ u8 buffer;
+ struct mutex lock;
+};
+
+static void pca9570_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
+{
+ struct pca9570 *gpio = gpiochip_get_data(chip);
+ u8 buffer;
+ int err;
+
+ mutex_lock(&gpio->lock);
+
+ buffer = gpio->buffer & ~mask;
+ buffer |= (mask & bits);
+
+ err = i2c_smbus_write_byte(gpio->client, buffer);
+ if (!err)
+ gpio->buffer = buffer;
+
+ mutex_unlock(&gpio->lock);
+}
+
+static void pca9570_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+ pca9570_set_mask_bits(chip, BIT(offset), value ? BIT(offset) : 0);
+}
+
+static void pca9570_set_multiple(struct gpio_chip *chip, unsigned long *mask,
+ unsigned long *bits)
+{
+ pca9570_set_mask_bits(chip, *mask, *bits);
+}
+
+static int pca9570_get_direction(struct gpio_chip *chip,
+ unsigned offset)
+{
+ /* This device always output */
+ return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int pca9570_direction_input(struct gpio_chip *chip,
+ unsigned offset)
+{
+ /* This device is output only */
+ return -EINVAL;
+}
+
+static int pca9570_direction_output(struct gpio_chip *chip,
+ unsigned offset, int value)
+{
+ /* This device always output */
+ pca9570_set(chip, offset, value);
+ return 0;
+}
+
+static const struct gpio_chip template_chip = {
+ .label = "pca9570",
+ .owner = THIS_MODULE,
+ .get_direction = pca9570_get_direction,
+ .direction_input = pca9570_direction_input,
+ .direction_output = pca9570_direction_output,
+ .set = pca9570_set,
+ .set_multiple = pca9570_set_multiple,
+ .base = -1,
+ .ngpio = 4,
+ .can_sleep = true,
+};
+
+static const struct of_device_id pca9570_of_match_table[] = {
+ { .compatible = "nxp,pca9570" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pca9570_of_match_table);
+
+static int pca9570_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct pca9570 *gpio;
+ int ret;
+
+ gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
+ if (!gpio)
+ return -ENOMEM;
+
+ i2c_set_clientdata(client, gpio);
+
+ gpio->chip = template_chip;
+ gpio->chip.parent = &client->dev;
+
+ gpio->client = client;
+
+ mutex_init(&gpio->lock);
+
+ ret = devm_gpiochip_add_data(&client->dev, &gpio->chip, gpio);
+ if (ret < 0) {
+ dev_err(&client->dev, "Unable to register gpiochip\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static const struct i2c_device_id pca9570_id_table[] = {
+ { "pca9570", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, pca9570_id_table);
+
+static struct i2c_driver pca9570_driver = {
+ .driver = {
+ .name = "pca9570",
+ .of_match_table = pca9570_of_match_table,
+ },
+ .probe = pca9570_probe,
+ .remove = pca9570_remove,
+ .id_table = pca9570_id_table,
+};
+module_i2c_driver(pca9570_driver);
+
+MODULE_AUTHOR("Sungbo Eo <mans0n@gorani.run>");
+MODULE_DESCRIPTION("GPIO expander driver for PCA9570");
+MODULE_LICENSE("GPL v2");
--
2.27.0
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